Powder of high resistivity is electrostatically applied onto a part to be treated by spraying the part with a stream of powder electrified by charges produced by pins connected to a high-tension DC generator.
The electrified powder adheres to the part under the effect of electrostatic forces. Subsequent heat treatment applied to the part makes it possible to transform the layer of powder into a finished coat of paint or vitrified enamel.
U.S. patent application Ser. No. 97,112, filed Nov. 20, 1979, now U.S. Pat. No. 4,304,764 describes a booth which includes electrodes brought to a high electric potential, said electrodes being disposed at the inlet and at the outlet of an electrostatic powder-deposition chamber, but this booth does not make it possible to obtain good results. Not all the powder is charged or the powder is insufficiently charged. As a result, a more or less large fraction of the powder is not deposited on the parts.
In a booth in accordance with French Pat. No. 2 442 080 powder not deposited on a part either falls directly through a sifter into a recovery tank situated at the base of the booth or else is directed towards filters disposed in inlet and outlet modules.
The present invention aims to increase the proportion of powder which is deposited on the parts to be treated.